The technical scope of the invention is that of ignition devices for the propellant charge of a piece of ammunition.
Known ignition devices implement an igniting pyrotechnic composition or a squib.
It is known to ensure ignition spaced over substantially the full length of a propellant charge by using a squib that ignites a primer tube formed by a stack of black powder tablets.
Patent FR2593905 describes such a primer tube. However, present day cased ammunition generally has projectiles of great length whose rear part or tail piece is housed near to the ignition means. It is thus impossible to install sufficiently long primer tube in such ammunition.
To solve the problem of igniting such loads it is known to use flexible igniting means in the form of pyrotechnic cords whose igniting action is both axial and radial.
Patent EP344098 describes such an ignition device. This device has the main disadvantage of implementing a cord enclosing a pyrotechnic substance. This substance may be accidentally ignited, conducting to the inadvertent ignition of the propellant charge.
Such a risk is even greater during the assembly and integration phases of a propellant charge.
Moreover, attempts are being made at present to increase the density of propellant charges, and therefore improve their firing performances, by implementing agglomerated loads.
So as to improve the firing ballistics, the time and place of the ignition of such agglomerated blocks has to be controlled. This is made difficult by the implementation of classical ignition cords that ensure ignition over their full length.
Lastly, the coming years will see an improvement in firing performances through the implementation of plasma igniters. These igniters use electrical energy to increase the temperature and pressure of the propellant gases, and thus the initial velocity of the projectile.
Known plasma igniters (or torches) have a cylindrical structure similar to that of a classical primer tube and are difficult to associate with ammunition in which the projectile penetrates deeply inside the propellant charge.
The aim of the present invention is to propose an ignition device that overcomes such drawbacks.
Thus, the ignition device according to the invention may be associated with ammunition incorporating a projectile penetrating deeply inside the charge.
The ignition device according to the invention may be installed without risk in a charge and it allows the ignition of an agglomerated charge to be precisely controlled.
Thus, the invention relates to an ignition device for a propellant charge, comprising at least one ignition means, such device wherein it incorporates at least one inert diffuser tube extending through part of the propellant charge and allowing the flame generated by the ignition means to be guided up to a receiver zone of the propellant charge.
The diffuser tube will preferably be made of a flexible plastic material and may be of a thickness of between 0.7 and 1.5 mm.
The diffuser tube may have an internal diameter of between 3 and 6 mm.
According to a particular embodiment, the ignition means can be electrical means generating a plasma (plasma torch).
Advantageously, the device may incorporate an expansion chamber placed between the plasma igniter outlet and the diffuser tube or tubes.
The invention also relates to a propellant charge incorporating such an ignition device.
This propellant charge will incorporate at least one block of agglomerated propellant powder, such block having at least one closed-ended ignition channel intended to receive a diffuser tube
According to a particular embodiment, the charge may incorporate at least two blocks of agglomerated propellant powder stacked on top of one another, a first block at least having an open-ended connecting channel intended to receive a diffuser tube through said first block coming to lodge in an ignition channel made in a second block.
Each block may thus incorporate three closed-ended ignition channels evenly spaced angularly and each intended to receive a diffuser tube.
According to another embodiment, the charge comprises at least three agglomerated blocks that each incorporate three closed-ended ignition channels evenly spaced angularly and intended to receive a diffuser tube, the block nearest to the igniter also incorporating six open-ended connecting channels and an intermediate block incorporating three open-ended connecting channels.